Conventional liquid crystal displays are often made up of a number of color or monochrome pixels filled with liquid crystal molecules and arranged in front of a light source (such as a backlight) or a light reflector. Each addressable pixel of the display includes a liquid crystal element arranged proximate to two electrodes. By setting a voltage between the two electrodes, the strength of an electric field between the electrodes is changed. The strength of this electric field causes molecules within a liquid crystal element to assume a specific orientation relative to the electric field (i.e., either parallel or perpendicular to the electric field, or at some angle in between). When combined with suitably oriented polarizers, a liquid crystal element effectively acts as a shutter, allowing a certain amount of light to pass out of the display at a respective pixel. Thus, by adjusting the voltage between the two electrodes, the display can produce various levels of grey (or in the case of color, various levels of red, green, or blue).
If the voltage between the two electrodes is held constant for an extended period of time, a phenomenon known as “image sticking” can occur. Image sticking is a result of a parasitic charge build-up within liquid crystals that prevents the liquid crystals from returning to their normal state after the voltage applied to the electrodes is changed. This can cause charged crystal alignment at the bottom or top of a particular sub-pixel, or even a crystal migration toward the edge of the sub-pixel. The net effect of image sticking is that a faint outline of a previously displayed image can remain on the display screen even after the image is changed. This effect is therefore undesirable.
Conventional inversion techniques correct this phenomenon by periodically switching the polarity of the voltage applied between the two electrodes. However, some of these inversion techniques yield image degradation and/or flicker, while others require hardware capable of supplying large output voltage ranges or otherwise require a high frequency of alternating voltage. For this reason, conventional inversion techniques often require a large amount of power to implement.